SOLID-STATE CONFORMATIONS OF MEDIUM-SIZED-RING PHOSPHORUS HETEROCYCLES: X-RAY CRYSTAL STRUCTURES OF TWO NORBORNENE-FUSED 1,3,2-DIOXAPHOSPHEPANES WITH EQUATORIALLY DISPOSED SUBSTITUENTS ON PHOSPHORUS

Abstract

Abstract The seven-membered-ring phosphorus heterocycles, frans-5,6-(endo,endo-2′,3′-bicyclo[2.2.1]hept-5′-eno)-2-oxo-2-phenoxy-1,3,2-dioxaphosphepane. trans-1, and trans-5,6-(endo,endo-2′,3′-bicyclo-[2.2.1]hept-5′-eno)-2-oxo-2-phenyl-1,3,2-dioxaphosphepane, trans-2, have been synthesized and the crystal and molecular structures of the compounds determined from single-crystal X-ray studies. Compound trans-1 crystallizes in the monoclinic space group P21/c with four molecules per unit cell of dimensions a=6.275(2) Å. b=19.419(7) Å, c=11.363(2) Å, and β=90.89(2)°. Full-matrix least-squares refinement using 2317 unique reflections having 2.5° ≤ 28 ≤ 49.0° and 1 ≤ 3 σ (1) converged at R=0.0543 and Rw=0.0650. Compound trans-2 crystallizes in the orthorhombic space group P212121 with four molecules per unit cell of dimensions a=9.702(3) Å, b=11.296(4) Å, and c=12.605(4) Å. Full-matrix least-squares refinement using 1862 unique reflections having 4.0° ≤ 20 ≤ 50.0° and 1 ≥ 2.5 σ (I) converged at R=0.040 and Rw =0.036. In both of these structures, the seven-membered ring heterocycle adopts a chair conformation with the substituent on phosphorus equatorial.